The present invention relates to a sail based on a multilayer composite film comprising a stretch-oriented, heat-set polyester film, in particular polyethylene terephthalate film.
The sail can be used for sports equipment which move on land, on water or in the air by means of wind energy. Sports equipment of this type includes, for example, beach gliders, sail boats, windsurfing boards, sail planes, hang gliders, ultralight planes and balloons.
Multilayered sails, in particular windsurfing sails, comprised of a biaxially stretch-oriented and heat-set polyester film which is adhesive-bonded to a fiber fabric, are known from EP-A-0,227,922. In contrast to sails made of woven fabrics, the sail films disclosed therein are airtight and result in an increased thrust. Moreover, the material is particularly well-suited for use as sails because of its high tear resistance.
Windsurfing sails made of plastic film, however, are subject to rapid aging and tend to become brittle when being frequently used. In particular, they exhibit an unsatisfactory resistance to tear propagation.